The present invention relates generally to articulated vehicles and more particulary to an articulated vehicle that has two frame sections, both of which have a pair of driven supporting wheels and a coupling or joint between the two frames to allow for relative rotation of the frames about both vertical and horizontal axes.
The recent trend in the design and construction of heavy earth moving equipment has utilized articulated vehicle sections that are pivotally interconnected and each section is supported by a pair of driven wheels. An articulated vehicle of this type is highly desirable since one section which houses the power plant can be a rather standard design and can be connected with a second section that supports the implement or tool and the tool supporting section is always properly oriented with respect to the direction of travel during earth working operations.
These particular vehicles are normally steered by interposing a drive means, such as a hydraulic fluid ram, between the two sections at a location spaced from the pivotal connection between the sections. Examples of this type of vehicle are shown in U.S. Pat. No. 3,038,619 and U.S. Pat. No. Re. 26,635. While these patents disclose a pivotal connection between the two frame sections, no provision is made for accommodating a change in angular position of the respective frame section with respect to each other in the longitudinal direction of travel. It will be appreciated that normally these types of vehicles are operated on extremely rough terrain and it is imperative that all four wheels remain in engagement with the ground at all times.
Thus, it has been proposed to provide a single center pivot articulated connection between the two frame sections that allows for pivotal movement of the frame sections along a vertical axis as well as along a generally horizontal longitudinal axis. Examples of this type of connection are shown in U.S. Pat. Nos. 3,299,982 and 3,521,719.
However, one problem encountered with a center joint connection between the respective frames is that a subframe is required to accommodate oscillation of the respective axles with respect to each other about a longitudinal axis. It has been found that such an approach has inherent disadvantages in that the center articulated joint requires extra mounting pivot points on the frames which results in a higher overall center of gravity for the unit to clear the various components which of necessity are incorporated into a vehicle of this type.
A further disadvantage of a single center joint connection between the frame sections is that it makes it more difficult for providing for the various connections of the components on the respective frame sections. For example, normally these units have a power plant located on one of the frame sections and have the material handling unit on the other frame section. Since most of the control functions are, of necessity, located on the frame section with the material handling unit thereon, provision must be made for interconnecting the power plant with the various components on the other section which is normally accomplished through hydraulic plumbing and electrical wiring. Also, since all four wheels are driven it is necessary to provide a driving connection between the two sections, which is usually done with a drive shaft. With a center articulated joint, it becomes difficult to find adequate space for passing the drive shaft through the connection between the frame sections.